Democrat Jon Ossoff is making a final push for an upset victory in Tuesday's special election, though he and his supporters are girding for a runoff in the race for the suburban Atlanta district if he fails to win.

"We'll be ready for anything," Ossoff said. "Ready to fight and win a runoff if necessary."

Most public polls show Ossoff in the low-to-mid 40s in the race. That's well ahead of the closest Republican but short of the majority-mark he needs to escape a costly June 20 head-to-head matchup against a potentially unifying GOP candidate.

His supporters are bracing for a second round, even if they express confidence that he could pull off a stunning victory on Tuesday. His campaign manager urged volunteers to ready for a runoff, and many said they were hunkering down.

"Of course I'm ready for the long haul," said Arteen Afshar, an 18-year-old Ossoff volunteer in Alpharetta. "I'm in it to win it. And we are putting in the work to make it easier in June."

One of 18 candidates on Tuesday's ballot, Ossoff was a little-known investigative filmmaker and former congressional aide when he entered the race in January. But an unprecedented fundraising haul and a jolt from President Donald Trump’s critics propelled him into the national spotlight.

The odds are stacked against him in the district, which spans from east Cobb to north DeKalb and has for decades been held by Republicans. In an interview, Ossoff said his numbers show him within "striking distance" of a win.

"Momentum is on our side," he said. "But special elections are unpredictable and we're prepared for any outcome. And we will be ready to fight and to win a runoff if it comes to it."

Once jittery Republicans sound increasingly confident they can keep Ossoff under 50 percent, thanks in part to a surge of attack ads from national groups that depict him as an inexperienced stooge of U.S. House Democratic leader Nancy Pelosi.

But even the most optimistic Republican warns that hard-to-predict turnout models, mixed with rainy weather that besieged parts of the district, add another dose of uncertainty.

Add to this unpredictable mix last-minute tweets from Trump, who won Georgia by 5 points but struggled in the district.

He tweeted five times about the race in the last three days, including an attack on Ossoff minutes before the polls in Georgia opened. He also recorded a robo-call calling Ossoff a Democratic puppet.

"We are going to fight twice as hard," said Martha Bernstein, an Alpharetta teacher. "Jon is our hope for the future. Jon is our world moving forward. We are going to fight twice as hard, and we're not going away."